RBS / Channeling study of Er doped GaN ® lms grown by MBE on Si 1 1 1 substrates

The in ̄uence of the Ga cell temperature on the quality of GaN ®lms grown by MBE on p-Si(1 1 1) substrates was studied for cell temperatures (TGa) in the range from 865°C to 922°C using the RBS/Channeling technique. The ®lms were in situ doped during growth with Er at a constant cell temperature. The ®lms show a strong dependence of the crystalline quality on the Ga cell temperature with the best ®lms grown at TGa ˆ 915 C. For temperatures TGa below 880°C the ®lms showed no channeling e€ect. The thickness increases linearly with the temperature suggesting that changes in the Ga ̄ux in ̄uence the growth process. The decrease of the Ga ̄ux allows the incorporation of higher Er concentrations in the ®lms. The data showed that a maximum value of about 0.35 at% was reached under the chosen growth conditions. The Er ions occupy mainly the Ga sublattice in the ®lms with single crystalline quality. A comparison of the angular scans through the á0 0 0 1ñ and the á1 0 1 1ñ axes with Monte Carlo simulations leads to the conclusion that a majority ( 90%) of the Er ions occupies Ga sites. Ó 2000 Elsevier Science B.V. All rights reserved. PACS: 81.05Ea; 81.15Hi; 81.70Jb